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Idiot test sat...

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amcboy

amcboy

Jedi Hopeful
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After fighting with my new scuttle seal for a few hours, actually fighting with the door, as the new seal was fine...

I decided that I was done and left for home.

Started up and shut my door and presto the IGN idiot light lit up... and then failed to go out as usual.

Obviously indicating an idiot at the wheel.

But I digress, I checked the wiring at the alternator and the device in question appeared to be fine when metered...

Then started the vigiorus wiggling of any and all brown and white wiring...

During the post-wiggling testing (right after reaching waaay up to the ammeter leads) the light went out (was hoping it was a bulb failure)!

So, figuring I'd aced the problem I got back in, backed out of the shop and closed the shop door, got back in the car and upon closing my door the @#$! @!#%! light came back on...

So after...(snip) this was getting long.

After more wiggling the light was persistent, and it was dark an 12 miles to home... (and I had no sunglasses)

Having done this kind of thing before, I went low beam only and instruments off (hard to see much change there) to reduce the load on the battery as much as possible...

Got home fine.(!) In fact the lights never dimmed and the coughing never started from a lack of 'trons...

Now, either my battery seriously kicks some butt, or somehow my idiot light is an idiot and all is well (except for the light of course)...

Anyone got any insights on this?

After consulting the schematics it appears that the light comes on when the V/R goes low and the 12v from the key-switch makes the trip...

I'm thinking cabling between the light and the alternator (a short to ground would light the light, if I'm reading the print right).

Unfortunately 5AM will be here much too early, so I'm off (more than usual) to bed.

I eagerly await your enlightened responses, or loads of derisive laughter! /bcforum/images/%%GRAEMLIN_URL%%/thumbsup.gif
 
After you've rested, I'm sure it will occur to you to check the alternator's output.
Coincidence that closing the door, and the light coming on,maybe? Then there is the seatbelt module with 12 terminals. Terminals #1 and #10 (door switch and ignition respectivly) may be worth a look.
 
A short to ground would definitely light the light, but would also mess up the operation of the alternator. It's hard to imagine that it would still be charging normally with that terminal grounded, since that terminal is used to sense the battery voltage.

I think this is a case where the solution is classical electrical troubleshooting--disconnect the idiot light lead at the alternator, and see if the light still lights. If so, there is a short in the wiring somewhere. Should not be hard to find, since you have it pretty well localized at that point.
 
Can't muster derisive laughs this AM, mebbe a moderate chuckle.

Sounds like you're in for a session with th' VOM and a schematic. Are ya burdened with the Lucas alternator or a replacement? Point bein': can ya isolate the diode bridge to check it? Brush pack easy to get to?
It just CAN'T be as simple as a shorted wire to th' bulb. /bcforum/images/%%GRAEMLIN_URL%%/jester.gif
 
You should be able to drive without the alternator for at least an hour or two (even with headlights), so 12 miles doesn't prove anything IMO. I've even commuted to work without one, by trickle charging every night.

As noted, I think you're in for some quality time with a DMM. Might even be you've got multiple problems ... maybe the alternator is bad and there's also a bad connection behind the dash ... might even be the bad connection is why the light went out /bcforum/images/%%GRAEMLIN_URL%%/grin.gif

What was the ammeter doing during all of this ?
 
Ayup, the alternator was indeed bad.

$70 at Autozone gets me a LLW Lucas re-man...

or $114 at TRF... no LLW...

whee!


BTW the ammeter was behaving "strange" during this. If you applied a load, say the blower, the load would register as a discharge that would creep back to zero...

I would have expected the load to stay registered as a discharge... (?)
 
regulator ~tryin' hard~ to "fix" things?
 
I'd sure want to give the wiring to the dash light the "hairy eyeball" before installing that new alternator ! There is clearly a problem in that area, and it's at least possible that a short to ground in the wire to the lamp is what caused the alternator to fail.

And, I wouldn't be at all surprised if your LLW doesn't cover damage caused by other problems with the car.

Not sure what's up with the ammeter creeping back up; but that might also be consistent with a short in the wire.
 
Uh, if I may,

One of the tests on an alternator output, should be a test with your meter set on "ac" volts.

I gotta fried chicken tv dinner that says he had half, or more of the diode pack decide that it had enough.

A high ac component on your charging circuit would give you the wonky ammeter readings.

Steve
71 MKIV

Lancaster PA

rotation and excitation make electrcity
 
Good call Steve.

I always check for an AC component when ancient diodes are involved.

Unfortunately this dude is dead...

Checked the wiring (metered and visual) and all seems well.
 
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